Refrigerating apparatus



March 12, 1946.

G. C. PEARCE ETAL REFRI GERAT ING APPARATUS Filed May 31, 1941 3Sheets-Sheet 1 6 F INVENTORS BY W O M March 1946- G. c. PEARCE ETAL.

REFRIGERATING APPARATUS Filed May 51, 1941 3 Sheets-Sheet 2 A. a w

I c FINVENTORS BY 0 3 Sheets-Sheet 3 Filed May 51, 1941 G. C. PEARCE ETAL REFRIGERATING APPARATUS March 12, 1946.

INVENTOR.

Patented Mar. 12, 1946.

UNITED STATES PATENT OFFICE REFRIGERATING APPARATUS George C. Pearce andAlbert 0. Grooms, Dayton, Ohio, assignors to General Motors Corporation,Day ton, Ohio, a corporation of Delaware Application May 31, 1941,Serial No. 395,934

'7 Claims.

This invention relates to refrigerating apparatus and more particularlyto control means therefor.

When the load is light it is found desirable to operate heating andcooling systems at a reduced capacity. To accomplish this two separate,ac-

curately matched thermostats have been used.

However, such thermostats provide no means for varying the differencebetween the two thermostats according to the season or other conditions.

It is an object of our invention to pr vide a single control forcontrolling two functions consecutively with means for varying bothfunctions together, and also relative to one another,

It is another object of our invention to provide a control with animproved adjusting and indicating device in which more than onerevolution of the adjusting device can be provided within the limits ofthe indicator.

It is another object of our invention to provide a means for reducingthe inherent differential of cycling in refrigeration controls.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, wherein a preferred form of the present invention is clearlyshown. 1

In the drawings:

Fig. 1 is a view partly diagrammatic of a coolingsystem provided with acontrol embodying one form of our invention;

Fig. 2 is a wiring diagram for the control and system shown in Fig. 1;

Fig. 3 is a sectional view of the control taken along the line 3-3 ofFig. 4;

Fig. 4 is a sectional view taken along the line 4-4 of Fig. 5;

Fig. 5 is a sectional view taken along the line 5-5 of Fig, 4; a

Fig. 6 is a sectional view taken along the line 66 of Fig. 4;

Fig. 'I is a vertical sectional view through the adjusting knob; and

Fig. 8 is a fragmentary top view of the adjusting mechanism and a dialwith the knob removed.

Briefly, we have shown a heat exchange system with a control foroperating the system at either part load or full load in accordance withthe demand. The control is provided with a single operating means inaccordance with temperature which operates two snap-acting deviceshaving independent differential adjustments. The operating means isdirectly connected to one lever operating one of the snap-acting deviceswhile this one lever is connected through an adjustable connection tooperate a second lever which in turn operates the second snap-actingdevice. The control is also provided with an additional operating bulbfor anticipating a change in temperature to reduce the overalldifierential of the system.

For'the purpose of illustrating one application of our improved form ofcontrol, we'have shown a refrigeration air conditioning system includinga compressor 20, driven by an internal combustion engine 22 forwithdrawing the evaporated refrigerant from an evaporating means 24through a suction conduit 26 and for forwarding the compressedrefrigerant to a condenser 28 where the compressed refrigerant isliquefied and returned to the evaporator 24 through the supply conduit30 under the control of a suitable liquid control device 32. Theevaporating means 24 is located within an air duct 34 which dischargesinto a room 36 or other enclosure to be kept cool. The air is drawn intothe duct at its entrance end 38 by an electric fan 40 which forces theair through the evaporating means 24 so that it is cooled.

For controlling the operation of the refrigerating system, we provide asuitable control device 42 which is principally responsive to the airwithin the enclosure 36. This control device includes a base 44 carryinga bellows 46 which operates a lever 50. The expansion of the bellows iscontrolled by a compression type coil spring 52 which has its tensionadjusted by a suitable adjusting screw 54 which is rotated by anadjusting knob 56. Heretofore in order to prevent the control becomingout of adjustment b the unrestricted adjustment of the knob it has beencustomary to limit the adjustable movement of the knob to onerevolution. This has made the adjustment either very limited in range orvery coarse. In order to provide a greater range and yet permit a fineadjustment, we have provided a means by which the knob 58 may beadjusted several revolutions without its adjustment being lost andretaining at all times an indication of its adjusted position.

In order to do this, we have provided a movable indicating plate 58which is connected to the adjusting screw 54 and the knob 56 through aform of gearing so that it will be limited in movement to one revolutionwhile the knob 56 may make two revolutions or more. 7 As will be bestseen in Figs. 7 and 3 the upper end of the screw 54 is provided with thesplined end 60 which may be fastened to the shank of the screw 54 byriveting. The knob 56 is locked to the splined end by a set-screw 62.The dial plate 58 is provided with a planetary pinion as which isrotatably mounted upon a rivet 66 fastened to the dial plate 58. Thisplanetary pinion [it meshes with the lower end of the splined portion 80and also with an internal gear-til which is fastened by the rivets tothe upper part of the switch frame member '12. The internal gear 68 isprovided with a segment I4 which is not provided with teeth so that therevolving movement of the pinion 64 is stopped when it strikes eitherend of the segment I4. As shown the splined end 60 is provided withtwelve teeth and the internal gear 68 with 42 teeth. This will allow theknob 58 to rotate several times during the revolving of the pinion 64from one end of the internal gear 88 to the other. The dial plate 58 isprovided with a suitable arrow indicating the adjustment of the controlby the knob 58. This arrow may cooperate with suitable legends providedupon the outer case I8 of the switch mechanism.

This control d ffers from ordinary controls in that a second lever 80 isconnected to the usual lever 50. This connection is made by an arm 82which is fastened to the lever 50 and extends over the second lever 00.The connection between the arm 82 and the lever 80 is made by a screw 84which extends through an aperture in the arm 82 and threads into athreaded aperture in the lever 80. A compression type coil spring 88 isprovided for keeping the arm 82 in engagee ment with the head of thescrew 84. The screw 04 may be turned to bring the lever 80 closer orfarther away from the arm 82 so as to change the relative positions ofthe levers 80 and 50.

Each of the levers are connected to identical snap-acting switchmechanisms. For this reason a detailed explanation will only be made forone switch mechanism. This connection is made by a molded member 88which is provided by the free end of the lever 50 and which supports adouble spring anchoring member 90. A pair of tension type coil springs92 and 94 connect the anchoring member 90 with ears 96 and 98 providedupon opposite sides of a metal member IOI having its opposite endriveted by an electrical contact member I03 to the free end of aflexible metal strip I05 having its opposite end anchored to a post I01.The springs 92 and 94 together with the members I M and I05 form anexcellent toggle snap-acting device having high currentcarryingcapacity. The differential of the toggle mechanism is controlled by aset screw I09 which controls the open position of the contact I03 whilethe closed position is controlled by the location of the contact postIII. An arm I I3 is provided for limiting the movement of the member 0|.

The snap-acting device connected to the lever 80 is identical and isalso provided with a differential adjusting screw II5. Thus thediil'erential of the two snap-acting devices may be adjusted by theirrespective screws I09 and H5 independently of each other so that theirdifferentials may be made either the same or diflerent as desired withinthe limits of the device. The screw 84 may be adjusted so as to vary therelative position of the two levers as desired. If the differentials arethe same the screw 84 may be adjusted so that both switches will openand close at the same time or so that one of the switches will precedeor succeed the operation of the other by any desirable amount of movement of the operating bellows 46. This same thing can also be done whenthe screws I09 and H5 are adjusted to two different differentials. Insuch a case, the" screw 8-3 can be adjusted so that one of the points ofoperation of one of the switches may coincide with a point of theoperation of the other of the switches. Also the range of one of theswitches may be either within or without the range or the other of theswitches. It will therefore be seen that there is provided freeflexibility in the control and adjustment of this control device.

The bellows 46 is connected by asuitable tube II! to a bulb II9'mountedin the incoming air stream of the duct 34 so that it is substantiallyresponsive to the temperature of the air within the enclosure 36.Preferably this bulb is filled with activated charcoal and the entiresystem is charged with methyl chloride or some other suitable gas whichis adsorbed and evolved from the activated charcoal in the bulb H9according to changes in temperature. The vapor pressure of the methylchloride should be sufficiently low to prevent free condensation at anypoint. However, the control 42 may be operated by any sort of operatingdevice operating in accordance with any volume which is the source ofcontrol.

We have found that snap-acting devices, though desirable for effectingthe operation of switch mechanisms, have a larger differential than isdesirable for some refrigeration applications. It is diflicult to reducethe differential of snap-acting mechanisms below a certain optimumwithout incurring certain disadvantages. We have discovered that if anadditional bulb I2I is placed in the air stream flowing away from theevaporating means 24, the overall differential may be reduced withoutchanging the diiferential of the snap-acting mechanisms. This additionalbulb I 2| is filled with the same material as the other bulb II 9, suchas activated charcoal and the methyl chloride or other gas used. Thismethyl chloride or other gas flows to and from the bulb I2I as well asto the remaining points of the system.

In operation the bulb II9 always follows the temperature of theenclosure 36 as accurately as possible. The bulb I2I when therefrigerating system is in operation is cooled below the temperature ofthe enclosure. When the refrigerating system is not in operation thebulb I2I returns to substantially the temperature of the air in theenclosure 36; In order to effect the operation of the switch mechanismfrom open position to closed position a predetermined volume of gas mustbe forced into the bellows 46. This is accomplished by a rise intemperature of both bulbs H9 and HI in accordance with the rise intemperature within the closure 36. This rise in temperature of thebulbs- H9 and I2I drives a certain amount of methyl chloride out of theactivated charcoal in the bulbs in accordance with the amount andquality of the activated charcoal present in each. When this temperaturerise is suflicient the bellows 46 will operate one or both switchmechanisms in accordance with the adjustment of the device.

In the wiring diagram shown in Fig. 2, the fan 40 is shown connectedacross the supply conductors I23 and I25 which connect to opposite sidesof a battery I 21 or some other suitable source of current supply. Thisfan motor is controlled by a manual switch I29 which also directly orindirectly controls the operation of the other electrical devices of theentire system. A second manual switch I 3| controls the operation of theremaining devices in the electrical system as long as the fan motoroperates. The control device is illustrated in the wiring diagram by thecontacts III and I03 operated by the lever 50 and the contacts I 33 andI35 which are operated by the lever 80 (see Fi 4).

It is intended that the screw 84 be so adjusted that the contacts II Iand I03 will be closed at a temperature which will require a relativelysmall amount of cooling such as one-third or one-half of fullrefrigerating capacity. For example, these contacts III and I03 may beset so that they will close at a temperature of 75 and open at atemperature of 73. The screw 84 may be so adjusted that the contacts I33and I35 will close when the temperature reaches 78. The closing of thecontacts III and IE3 will close the ignition circuit of the internalcombustion engine 22 including the ignition coil I37 and the distributorI39. It will also close the circuit through the relay I4I which willclose a starting switch I43 to energize the starting motor, I45 to startthe internal combustion engine 22. Connected in series with the startingrelay MI is a suitable automatic switch I 41 which will deenergize thestarting motor I45 whenever the engine is in normal operation. Thus theclosing of the contacts III and H13 insures the operation of theinternal combustion engine 22 which drives the compressor 20.

The internal combustion engine 22 is provided with an electricallycontrolled throttle I49 which, when deenergized, causes the internalcombustion engine 22 to be throttled and operate at a reduced speedsupplying refrigeration at a reduced capacity. When the refrigerationload increases the bellows 46 will expand further to cause the closingof the contacts I33 and I35 to energize the electrically operatedthrottle I49 to fully open the throttle of the internal combustionengine so as to cause it to operate at full speed. Should this reducethe temperature sufilciently, the contacts I33 and I35 will open therebyreducing the speed of the internal combustion engine. In normaloperation, the internal combustion engine under heavy loads will cyclebetween full load and part load while under lightoperating conditions itwill cycle between a part load and a stopped condition.

When the refrigeratingsystem operates the bulb I2I will be cooled belowthe temperature of the bulb H9 and the average air temperature withinthe enclosure 36. This additional cooling of the bulb I2I tends toreduce the overall differential of the control mechanism since it willreduce the amount of free methyl chloride in the actuating system belowthe amount which would be there at the actual air temperature of theenclosure. Therefore this excess cooling of the bulb I2I will providethe same effect as cooling the bulb II9 a certain amount below theactual temperature of the room prior to any actual reduction of thetemperatur of the room or enclosure. However, since the bulb H9 isactually at the same temperature as that of the room its temperaturewill fall as the room temperature falls; but as soon as the bulb I2I hasbeen immediately cooled a certain sizeable amount by the eil'ect of thecooled air coming directly off the evaporator 24, a much smaller amountof cooling of the bulb II!) will be required before the bellows 45 hascontracted an amount sufllmuch of the diflerential can be removed asdesired.

While the form of embodiment of the invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows: a

1. A control including an operating means, a control device connected toand operated by the operating means, an adjustment mean for the controlincluding a manipulating means, an indicating means, a direct ratiospeed changing device operatively connecting the manipulating means andthe indicating means to provide movements of the indicating meanscorresponding in a direct ratio to the movement of the manipulatingmeans, and means for limiting the movement of the indicating means. 1

2. Refrigerating apparatus including a cooling unit, supply means forsupplying a cooling mecient to overcome the difierential of the switchmechanism to open the contacts. By properly proportioning the amount ofcharcoal in the bulb dium to the cooling unit, cyclical control meanshaving an inherent differential for cyclically controlling said supplymeans, means for circulating a medium to be cooled in heat exchangerelation with the cooling unit, means responsive primarily to thetemperature of the medium flowing to the cooling unit for controllingsaid cyclical control means, and means responsive primarily to the'medium flowing away from the cooling unit for reducing the inherentdifferential of the cyclical control means.

3. Refrigerating apparatus including a cooling unit, supply means forsupplying a cooling medium to the cooling unit, cyclical control meanshaving an inherent differential for cyclically controlling said supplymeans, means for circulating a medium to b cooled in heat exchangerelation with'the cooling unit, a fluid motor for operating the cyclicalcontrol means, a main bulb means responsive primarily to the mediumflowing to the cooling unit, a compensating bulb means responsiveprimarily to the medium flowing away from the cooling unit for reducingthe inherent difierential of the cyclical control means, meansconnecting said bulb means with saidmotor, and means within the bulbmeans, connecting means and "said motor for creating pressures thereinsubstantially in accordance with the volume and temperature of the bulbmeans.

4. A control including an operating means, a control device connected toand operated by the operating means, an adjustment means for the controlincluding a manipulating means, an indicating means, direct ratio speedreducing planetary gearing operatively connecting the manipulating meansand the indicating means to provide movements of the indicating meanscorresponding in a direct ratio to the movement of the manipulatingmeans, and means for limitting the movement of the indicating means.

5. Refrigerating apparatus for an enclosure containing a medium to becooled comprising a cooling unit for cooling said medium, supply meansoperable at part load and full load for supplying a cooling fluid tosaid cooling unit, and control means including means responsiveprimarily to the temperature of the medium in said enclosure and alsomeans cooled by said Y cooling unit for varying the operation of saidsupply means between part load and full load.

'6. A control including a single operating fluid motor, a first leveroperated by said motor, a first toggle snap-acting means operated bysaid first lever and having critical opening and closing points, meansfor adjusting said first toggle means to vary one of said pointsindependently of the other, a second lever having its pivotsubstantially in alignment with the pivot point of the first lever, asecond toggle snap-acting means operated by said second lever and havingcritical opening and closing points, means for adjusting said secondtoggle means to vary one of said points independently of the other, afirst control device operated by said first toggle means, a secondcontrol device operated by said second toggle means, connecting meansbetween the two levers, means for adjusting the connecting means to varythe relationship between the levers to vary the relationship between theoperation of the control devices, and adjustable spring means actingupon said fluid motor to vary the relationship between the pressurewithin the fluid motor and the operation of the control devices.

7. Refrigerating apparatus for an enclosure containing a medium to becooled comprising a cooling unit for cooling said medium, supply meansfor supplying a cooling fluid to said cooling unit, cyclical controlmeans for cyclically controlling the supply means including a controldevice and an expansible chamber operating means operably connected tothe control device, said control means having an inherent operatingdiiierential, means including a main thermostat bulb connected to theoperating means and responsive primarily to the temperature of themedium in said enclosure for controlling said cyclical control means,and means including a smaller thermostat bulbconnected t0 the operatingmeans, said smallerbulb being cooled by said cooling unit and being sosmall in relation to the main bulb and the amount of change in volume ofthe operating means required to operate the cyclical control means as tobe incapable alone of opera ing the cyclical control means for reducingthe inherent diflerential 01 the cyclical 20 control means.

GEORGE C. PEARCE. ALBERT 0. GROOMS.

